The present invention relates to apparatus for processing paper sheets or the like, and more particularly to improvements in appaaratus for processing sheets which form a so-called scalloped stream wherein successive sheets partially overlap the preceding sheets. Still more particularly, the invention relates to improvements in apparatus for changing (when necessary) the spacing between the leaders of successive sheets in a continuous stream of partially overlapping sheets. Each such sheet can constitute a single layer, a folded sheet wherein the fold line is normally located at the leading end, or a group (e.g., a signature) consisting of three or more overlapping leaves.
It is well known to advance a stream of partially overlapping paper sheets or the like by a transporting unit (for example, an endless belt conveyor) which is caused to move stepwise through distances or increments of predetermined length, namely, through distances which correspond to the desired or required spacing between the leaders of successive sheets. Reference may be had, for example, to German Offenlegungsschriften Nos. 25 18 373 and 26 17 975. The prior publications disclose grippers or entraining elements which are adjacent to the path of movement of the stream of partially overlapping sheets and are movable into engagement with the sheets of such stream. The entraining elements or grippers are thereupon moved relative to each other by a worm wheel or a like displacing device so as to be spaced apart by distances corresponding to the desired spacing between the leaders of successive sheets of the stream. Once the stream has been treated, the grippers or entraining elements are disengaged therefrom and are moved back to the forward end of the portion of the path of movement of the stream where the action of establishing uniformity begins. The path along which the grippers or entraining elements move includes a magazine for temporary storage of superfluous sheet engaging devices. A drawback of such conventional apparatus is that their initial and maintenance costs very high and also that their space requirements greatly exceed the availability of space in many types of sheet processing plants. For example, such plants can employ newspaper printing and assembly machines or apparatus which assemble sheets into signatures prior to binding of signatures to form pamphlets, brochures, books or similar products.